A liquid crystal display device includes a control device and a display panel. In the display area of the display panel, basically, a plurality of pixels are arranged in a row direction (X-direction) and a column direction (Y-direction). The X-direction intersects the Y-direction. In recent years, various types of display panels have been available to consumers. The display panels are broadly divided into display panels which perform monochrome display (monochrome display panels) and display panels which perform color display (color display panels). Some monochrome display panels can perform gradation display. However, other monochrome display panels cannot perform gradation display. Some color display panels comprise a red (R) filter, a green (G) filter and a blue (B) filter as color filters. Other color display panels comprise a white (W) filter in addition to a red (R) filter, a green (G) filter and a blue (B) filter.
The dot display units of display panels are realized by pixels. The dot display pixels of monochrome display panels are simply referred to as pixels (or monochrome pixels). The dot display pixels of color display panels are referred to as subpixels. To display various colors, some color display panels comprise a red (R) subpixel, a green (G) subpixel and a blue (B) subpixel. Other color display panels comprise an R subpixel, a G subpixel, a B subpixel and a white (W) subpixel.
The use efficiency of light of W subpixels is higher than that of R, G and B subpixels. The transmittance of W subpixels is approximately three times that of R, G and B subpixels. Thus, the brightness of the display panel can be increased by using W subpixels.
Many external devices which supply video data (in other words, image data) to a liquid crystal display device output R, G and B video data items. In the future, various types of external devices will appear. For example, an external device may output monochrome video data as video data. Another external device may output R, G, B and dummy video data items.
As described above, various types of external devices and display panels will be present in the coming years. When a system for loading video data from an external device and displaying the data in a liquid crystal display device is designed, the type of one of the external device and a display panel is determined by the type of the other one of the external device and the display panel.
However, if the system is designed in the above manner, the finished system lacks flexibility. For example, when the external device is replaced by a new one, the new external device may not conform to the display panel of the liquid crystal display device. Conversely, when the liquid crystal display device is replaced by a new one, the new liquid crystal display device may not conform to the external device.